1. Field of the Invention
The present invention relates to a method for trimming spacers and a gate structure. In particular, the present invention relates to a method for trimming spacers to eliminate defects and a gate structure made from such method.
2. Description of the Prior Art
In the manufacturing process of semiconductors, a pair of protective and self-aligning spacers is formed to surround the elements of the semiconductor devices, such as the gates. However, when the spacers are formed, some undesirable side effects happen.
First, the newly formed spacers surrounding the gates make the substrate suffer new stress, in particular at the border of the spacers and the substrate. If the stress has incorrect direction or magnitude, the stress then has adverse influence on the elements in the substrate and on the carrier mobility in the gate channel.
Second, the newly formed spacers surrounding the gates may change the nature of the substrate. For example, the dislocation resulted from the new formation of the spacers may break or mess up the original arrangement of the silicon atoms in the substrate. Even more, the dislocation which breaks or messes up the original arrangement of the silicon atoms in the substrate results in defects and cracks. Later, when salicides are formed, the metallic atoms may take the opportunity to make their way into the substrate along the cracks formed by the dislocation, called salicide piping, and even go further ahead toward the gate channel. As a result, the leak current of the elements increases, the dislocation jeopardizes the performance of the elements and takes its toll on the electronic properties of the MOS.
Therefore, a technical solution is needed to relieve the adverse influence of the spacers on the substrate and to keep the semiconductor elements in good condition.